油气井井筒系统可靠性评价方法与应用

为了保障油气井尤其是高温高压含腐蚀性流体油气井的安全长效生产,针对油气井井筒结构设计的可靠性开展研究。利用可靠性原理,通过分类分析典型油气井井筒部件构成,开展井筒可靠性定量分析方法设计,建立了油气井井筒系统可靠性框图和井筒部件、系统可靠性定量分析数学模型;采用该分析方法对Y油田进行井筒系统可靠性定量估评,估评结果表明:如果采用针对性的措施工艺设计,该油田井筒系统可靠度在投产十年后为0.794 8,与常规设计相比可靠度提高165.64%;评估结果可为Y油田井筒系统设计提供参考;从应用情况来看,与预计情况相符。     

山区农村居民点空间分布特征与空间重构研究

梵净山地区地属喀斯特山区,其核心区为国家级自然保护区,村庄规划布局的制约因素较多。为实现农村居民点的空间优化,综合评价了农村居民点的空间位置、自然资源和区位条件对农村居民点分布的影响,利用主成分分析法综合各影响指标,求出农村居民点规模值,在此基础上通过基于断裂点的加权Voronoi图分割其作用范围,结合"居住场势"分类,找出需要搬迁的农村居民点。结果表明:1研究区共有农村居民点23 046个,面积14 342.78 hm~2,居民点多沿道路支线和河流分布于山间河谷地带,布局散乱。2区域内有零星居民点7 871个,面积为2 641.75 hm~2,占18.42%;需保留居民点10 288个,面积为5 680.46 hm~2,占39.6%;中心居民点4 887个,面积为6 020.57 hm~2,占41.98%。3空间布局优化后的农村居民点共15 175个,总面积不变,主要应将西部和梵净山保护区内的零散聚落向东部水源充沛、交通发达的集镇地区搬迁。研究成果可为梵净山地区新农村规划的科学编制提供理论参考。     

产品环境试验顺序的优化选择

首先介绍了产品进行环境试验的目的及其重要性,对环境试验项目之间的相互影响及合理顺序进行了分析,并阐述了选择环境试验项目顺序所遵循的一般原则,说明在进行环境试验时,必须针对具体试验项目,注意合理的试验顺序,才能确保试验结果的真实性、代表性和可比性。     

Hydrochemical Changes Over Time in the Zahedan Aquifer, Iran

Groundwater in the Zahedan Aquifer located in the arid southeast of Iran was chemically characterized to understand both the nature of the alluvium aquifer and the effect of human activities, specifically sewage disposal on groundwater quality. Concentrations of major cations and anions in the Zahedan Aquifer are much higher than concentrations observed in groundwater of similar settings. Although the nature of the aquifer and climatic parameters have affected the chemistry of groundwater, human impacts on the groundwater quality are more significant. The electrical conductivity in some areas of the Zahedan aquifer increased up to 7,500μS/cm in 25 years. Human influences in some areas are so prevalent, that the groundwater type changed from a Na⁺-HCO₃ ^- in 1976 to a Na⁺-Cl^- type in 2000. The impact of human influences on the groundwater quality is also indicated through observed nitrate concentration up to 4.81 meq/L in the urban area.     

Probabilistic Modelling of Cattle Farm Distribution in Australia

A probabilistic Bayesian method called weights of evidence (WofE) was used to develop a synthetic dataset of cattle farm locations at a national scale across Australia. The synthetic dataset was required for the modelling of livestock movements with a view to assessing biosecurity implications. The WofE method is based on the analysis of spatial relationships between evidential patterns with respect to an event, such as the actual location of a farm. The evidential patterns of cattle farms were derived from maps of land use, land tenure, drainage systems, roads, settlements and long-term averaged rainfall. These evidential patterns were used for delineating and ranking land areas suitable for cattle farming. For each evidential pattern statistics such as a positive weight, a negative weight and a contrast were calculated for estimating the degree of correlation between the evidential patterns and known farm locations. The integrated evidential patterns of known farms were then used for estimating posterior probabilities and splitting land into five different classes according to its suitability for farming.

国内70年来员工不安全行为研究:发展阶段、研究热点及趋势分析

为回顾和总结新中国70年来的不安全行为研究,推动具有中国特色的安全行为管理理论研究,基于新中国70年国内员工不安全行为领域的564篇文献,运用文献计量与Citespace知识图谱分析工具,分析我国员工不安全行为研究成长规律,构建作者和研究机构共现图谱,识别出该领域主要作者、机构及其合作网络特征.研究结果表明:我国员工不...     

贵阳市2种不同类型草地的汞释放通量

利用动态通量箱法对贵阳市人工草坪和天然草地的汞释放通量进行了野外实测. 结果表明:春季和夏季的草地是大气中汞的来源,并未出现明显的季节性变化,其平均汞释放通量为(7.8±15.7)～(41.5±15.2) ng/(m2·h),且天然草地的汞释放通量明显高于人工草坪. 草地的汞释放通量具有明显的日变化特征,白天汞释放通量显著高于夜间,最大值通常出现在午后,最小值则出现在夜间. 草地的汞释放通量与光照强度、土壤温度、大气温度呈显著的正线性关系,与大气相对湿度呈负线性关系. 大气中气态总汞的质量浓度是影响草地汞释放通量的另一个重要因素. 大气中气态总汞质量浓度的升高能够抑制草叶片向大气中释放汞,而高质量浓度的气态总汞可导致大气中的汞向草叶片的强烈沉降.      

土壤性质在出生缺陷环境风险中的指示作用

为研究土壤性质在出生缺陷环境风险中的指示作用,考虑了区域人口分布和疾病空间结构,使用Bayesian方法,对山西省和顺县连续4年的神经管畸形发生的数据进行了处理,并使用非参数统计的方法,结合土壤环境过程机理,对土壤的理化性质和出生缺陷的环境风险做了系统分析. 结果表明:土壤的机械组成,阳离子交换量(CEC),pH,有机质含量及碳酸钙含量都与神经管畸形发生率显著相关. 土壤砂粒含量高的地区,神经管畸形发生的风险会显著增加;土壤粘粒含量高的地区,神经管畸形发生的风险会显著降低. 土壤阳离子交换量高的地区,神经管畸形发生的风险会显著降低. 在偏碱性土壤且pH较高的地区,神经管畸形发生的风险会显著降低.在有利于土壤提供有效形态重金属及稀土元素的环境条件下,神经管畸形发生率会显著提高.在影响神经管畸形发生的环境因素中,土壤介质中各形态元素的有效含量比其总量具有更强的指示作用.      

Recovery or decline of the northwestern Black Sea: A societal choice revealed by socio-ecological modelling

During recent decades anthropogenic activities have dramatically impacted the Black Sea ecosystem. High levels of riverine nutrient input during the 1970s and 1980s caused eutrophic conditions including intense algal blooms resulting in hypoxia and the subsequent collapse of benthic habitats on the northwestern shelf. Intense fishing pressure also depleted stocks of many apex predators, contributing to an increase in planktivorous fish that are now the focus of fishing efforts. Additionally, the Black Sea's ecosystem changed even further with the introduction of exotic species. Economic collapse of the surrounding socialist republics in the early 1990s resulted in decreased nutrient loading which has allowed the Black Sea ecosystem to start to recover, but under rapidly changing economic and political conditions, future recovery is uncertain.     

Hierarchical spatial point process analysis for a plant community with high biodiversity

A complex multivariate spatial point pattern of a plant community with high biodiversity is modelled using a hierarchical multivariate point process model. In the model, interactions between plants with different post-fire regeneration strategies are of key interest. We consider initially a maximum likelihood approach to inference where problems arise due to unknown interaction radii for the plants. We next demonstrate that a Bayesian approach provides a flexible framework for incorporating prior information concerning the interaction radii. From an ecological perspective, we are able both to confirm existing knowledge on species’ interactions and to generate new biological questions and hypotheses on species’ interactions.